A Ka-band CMOS power amplifier using new substrate-shielded coplanar waveguide

A Ka-band three-stage power amplifier was developed in 0.18 mu m CMOS technology using a new substrate-shielded coplanar waveguide (CPW). The new CPW structure reduces the loss from the conductive silicon substrate allowing high gain for the amplifier. Broadband modeling of substrate-shielded CPW in conjunction with the RF transistor model tip to 40 GHz resulted in accurate gain matching of the amplifier. The power amplifier achieved a 12 dB small-signal gain at 26.5 GHz, which is the highest,for Ka-band CMOS power amplifiers using common-source transistors. The measured output power was 12.5 dBm with a power-added-efficiency of 8% at 26.5 GHz. These results show that scaled-down CMOS technology is a viable option for low-cost microwave and millimeter-wave circuits. (c) 2008 Wiley Periodicals, Inc.